In conventional seatbelt retractors, a sudden deceleration state of a vehicle is detected by a sensor, whereupon a spindle is rotated in a retraction direction by a motor. When there is a possibility of a collision, a seatbelt is retracted by a prescribed amount so as to lightly restrain an occupant often (referred to as “pretensioning”) and, when a collision occurs, an explosive pretensioner is operated so as to forcibly retract the seatbelt referred to as pretensioning, whereby the occupant is securely protected.
Further, in seatbelt retractors, a power transmission mechanism for transmitting power from a motor to a spindle is provided with a clutch mechanism which transmits power from the motor to the spindle/interrupts the transmission of power from the motor to the spindle in order to prevent rotation on a spindle side from being transmitted to the motor due to the operation of the pretensioner.
For example, in the seatbelt retractor described in Japanese Patent Publication No. 2011-162157, a pawl arranged in a pawl sliding groove of a gear wheel is used to engage/disengage a clutch housing and a gear wheel arranged so as to oppose each other, thereby switching between transmission and interruption of power of a motor which rotates the gear wheel. In addition, the pawl is held, via a friction ring, in an outer gear cover which houses the clutch housing and the gear wheel. As shown in FIG. 11(a) to FIG. 11(c) provided with this specification, the prior art teaches a friction ring 142 for holding a pawl has a plurality of claw portions 142b, each having a substantially hemispherical protruding portion 142c which protrudes towards an outer side in a radial direction. The claw portions 142b are pressed against a convex portion 126a provided on an outer gear cover 126 and the protruding portions 142c are brought into contact with an inner peripheral surface of the convex portion 126a, whereby the friction ring 142 is held on the outer gear cover 126 due to frictional force.